* The Coast Guard sends its icebreakers to clear a path through frozen waterways for free.
* The Pentagon pays its bills too fast, losing millions a year in interest.
* The Department of Housing and Urban Development (HUD) spends $8 to record a mortgage payment - a job private financial institutions do for around $1.50.
* The Federal Highway Administration keeps 185 real estate specialists on the payroll to appraise and purchase land for new highways, even though the Interstate Highway system is largely complete.
These are but a few examples of United States government activities labeled ''waste'' by the President's Private Sector Survey on Cost Control. The PPSSCC, a team of private citizens headed by businessman J. Peter Grace, on Monday released its second salvo of cost-cutting suggestions for the federal budget.
The recommendations - covering government cash management techniques, health care programs, and the Departments of Transportation, Interior, and Housing and Urban Development - would slash $76 billion off the budget deficit over the next three years, estimates the PPSSCC.
The group's first set of reports, released April 5, covered different agencies and contained an estimated $54 billion in savings.
The 1,300 members of the PPSSCC, most of them corporate executives, have been working for more than a year to identify areas where a dose of private-sector management techniques might save Uncle Sam money.
The specter of ever-increasing deficits means ''you really are going to have to do these things ultimately,'' says Mr. Grace, chairman of W. R. Grace & Co. and head of the panel. If current trends continue, he says, the deficit will be
Not all the group's suggestions, however, are new. The PPSSCC recommends that services such as icebreaking and rescues in non-life-threatening situations. Such fees have already been proposed by the Reagan administration and rejected by Congress.
''How high does the deficit have to get before yacht owners have to pay for these things?'' grouses Grace.
His panel's second round of reports also recommends that the Davis-Bacon Act, which requires that construction workers on government contracts be paid at prevailing union wages, be scrapped, and that the Clean Air and Clean Water Acts be modified to reduce government regulations. All these items have been listed before on the Reagan administration's agenda, but resisted by lawmakers.
But the biggest cut recommended Monday by the PPSSCC has already, in part, been adopted: prospective payment for medicare patients. Under such a system, the government pays hospitals a predetermined fee based on a patient's problems, instead of simply being billed for all costs incurred. The move would save $5.6 billion over the next three years, estimates the PPSSCC.
The social security bill passed by Congress last month contained a provision mandating prospective payment for medicare. The PPSSCC, however, recommends going further than current law by including doctor fees and privately insured patients in such a system.
Other suggestions contained in the second round of reports:
* An overhaul of government cash management techniques. Slowing down the Department of Defense bill payment rates, for instance, could save $2.5 billion by 1985. Increasing the use of electronic fund transfers could save $1.6 billion over the same period. Improving debt collections might bring in over $8 billion.
* Safety research by all federal agencies that deal with ground travel, such as the Federal Highway Administration and the Urban Mass Transportation Administration, might be combined in a new, separate agency. Five hundred-twenty research jobs would be eliminated, at a savings of $13 million.
* More thorough scrutiny of applicants for HUD housing assistance. A computer-matching program to catch those who aren't really eligible for such help could save almost $2 billion by 1985.
* Selling off excess government land (another move the White House is already attempting) would bring in $900 million.